Water bath shell egg pasteurization method

ABSTRACT

A batch processing control system for a shell egg pasteurizer controls the time and temperature in which batches of shell eggs are held in a pasteurization bath in accordance with a predetermined pasteurization protocol for designated egg size and start temperature. The predetermined pasteurization protocol is preferably statistically verified to optimize batches of eggs having the designated size and start temperature. The system also includes reporting software that generates daily reports to track each respective batch and verify that the batch has been pasteurized according to the statistically verified protocol.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.12/792,409 filed Jun. 2, 2010.

FIELD OF THE INVENTION

The invention relates to shell egg pasteurization systems, and inparticular the control of such systems to optimize the pasteurizationprocess in accordance with predetermined statistically verifiedpasteurization protocols. The invention also pertains to data reportingfor verifying that each batch of eggs has been pasteurized according tothe predetermined protocol.

BACKGROUND OF THE INVENTION

The Assignee of the present application owns several patents pertainingto the pasteurization of shell eggs including for example Cox et al.U.S. Pat. No. 5,589,211, and Davidson U.S. Pat. No. 6,322,833, each ofwhich is incorporated herein by reference. In general, commercializedpasteurization processes involve the use of a fluid pasteurizationmedium, such as heated water, heated oil, heated air or steam. In somesystems, batches of shell eggs are submerged into a heated bath andmoved sequentially from zone to zone in order to complete thepasteurization process. Other systems do not move the batches of eggssequentially through the bath but hold each batch in place for theduration of the pasteurization process. Certain aspects of the presentinvention apply to both types of systems. In either case, the purpose ofthe process is to heat the entire mass of the egg such that the centerof the egg yolk warms to an adequate temperature for a sufficient amountof time to pasteurize the egg and meet or exceed an accepted standardfor reduction of Salmonella Enteriditis without cooking the egg. A 5 logreduction in salmonella is the regulated standard set by the FDA for ashell egg to be labeled as pasteurized. In some cases, it may bedesirable to achieve at least a 7 log reduction or more. Also in somejurisdictions, a lower standard such as 2 or 3 log reduction may beacceptable. Pasteurization has been shown to kill other food bornpathogens as well. After pasteurization, the eggs can optionally becoated with FDA approved food-grade wax or other sealant containingantibacterial properties to further protect the eggs from outsidecontaminants. After pasteurization and sealing, the exterior of the eggsare dried, cooled and packed for storage, preferably at or below 45° F.It is typical to label the pasteurized eggs as pasteurized.

Once pasteurized, the eggs are safe for consumption even if raw orpartially cooked. It is still recommended, although not required by U.S.regulations, to refrigerate pasteurized eggs during shipment and storagein order to extend shelf-life and to maintain high egg quality andfunctionality. Conversely, unpasteurized eggs are required by U.S.regulations to be refrigerated because they are a potentially hazardousfood which poses a recognized salmonella health risk. Pasteurized shelleggs, on the other hand, no longer carry significant quantities ofsalmonella because the pasteurization process destroys all or almost allof the bacteria.

Just as it is important to uniformly heat the entire mass of the egg toa given temperature for the required period of time, it is alsoimportant not to overheat the egg during the pasteurization process.Overheating can result in partial cooking or loss in the quality andfunctionality of the egg. There are many methods for measuring eggquality and functionality, see for instance the methods discussed inabove incorporated U.S. Pat. No. 6,322,833. One of the most commonfunctionality tests is the albumen functionality test which measures eggwhite quality in Haugh units. As an egg ages, the thick portion of theegg white tends to thin. Haugh units are calculated using both the eggweight and the height of the thick albumen. Standard Haugh unit valuesfor different grades of eggs are follows: Grade AA is greater than 72Haugh units, Grade A is between 60 and 72 Haugh units, and Grade B isless than 60 Haugh units. The USDA (United States Department ofAgriculture) requires that all eggs for human consumption be graded bothin terms of weight (minimum weight requirements for applicable size,Medium, Large and Extra-Large) and quality (Grade AA, Grade A, Grade B).

One of the primary difficulties presented with shell egg pasteurizationis that eggs come in different sizes, weights and have different heattransfer characteristics. For example, the time in which an extra largeegg is required to be submerged within a water bath at a giventemperature for pasteurization (e.g. to achieve a 5 log reduction insalmonella) would likely partially denature the albumen or at leastcompromise the functionality of a medium sized egg. In addition todifferent egg size and quality, the starting temperature of the egg atthe beginning of the pasteurization process must be taken into accountas well. For this reason, it may be desirable to let refrigeratedbatches of eggs stand at room temperature or in a warming bath prior topasteurization.

In prior art batch processing pasteurization equipment using a heatedwater bath, each batch contains many dozens of eggs typically arrangedin flats and stacked one upon another, for example, as described in U.S.Pat. No. 6,113,961 which is also incorporated herein by reference. Thedesign of the flats facilitates effective, even access of heated waterto the eggs physically located in the middle of the batch. Pressurizedair can be supplied through openings into the water bath to causeperturbation and facilitate effective heat transfer as also discussed inthe U.S. Pat. No. 6,113,961. In one prior art system, each batch of eggsis held in a carrier that is supported by a gantry located above thewater bath and is moved in three (3) stages through each of four (4)zones in the water bath. An advance motor moves the respective carrierssequentially from stage to stage and zone to zone at fixed timeintervals.

FIG. 1 illustrates a prior art temperature control system 10 for apasteurizer water bath. The system 10 includes a programmable logiccontrol (PLC) 12 that controls the temperature within each of the zones14 in the pasteurizer water bath. FIG. 1 schematically depicts the PLC12 controlling the water temperature in one of the zones 14 in the waterbath. Temperature sensors 16 are located within the water bath in eachzone 14, and provide temperature signals to the PLC 12. Heating coils 18are located in each zone 14 of the water bath. The PLC 12 controls theoperation of a boiler 20 and a control valve 22 to provide heat to therespective heating coils 18 when required. The set temperature for thePLC 12 is different depending on the size of the eggs, e.g. medium sizedeggs have a lower set temperature than large or extra large eggs. Thelevel of air pressure and the motor advance rate are not controlled bythe PLC 12, and are generally fixed and not changed after the system 10has been installed and set up for operation. The system 10 also includesa water level sensor 24 that provides a signal to the PLC 12. When thewater level in the water bath 14 falls below the sensor level 24, thePLC 12 opens valve 26 to add cold water to the water bath. The system 10and the PLC 12, however, do not control the cold water valve 26 inresponse to the temperature sensor 16. In the prior art system 10, thePLC 12 is able to communicate with a computer 28 to allow an operator orsupervisor to view data on the PLC 12, e.g., check alarm status toensure that the system 10 is operating properly and that the temperaturein any given zone has not drifted outside of a desired temperaturerange.

As mentioned, a batch of medium eggs weighs substantially less than abatch of large eggs or extra large eggs, and hence will havesignificantly lower thermal capacity. When a batch of eggs is introducedinto the water bath, it immediately absorbs a large amount of energybecause of the large temperature difference between the eggs and thewater bath temperature. As the batch of eggs warms to or near the waterbath temperature, the speed and the amount of heat transfer from thewater bath to the eggs lessens. However, large and extra large eggstypically have more of an impact on the bath temperature in the initialzone than medium sized eggs, and the start temperature (e.g.refrigerated or room temperature) of the batch of eggs also has asignificant impact on the temperature in the initial zone.

One object of the present invention is to provide the ability topasteurize shell eggs not only at optimized bath temperatures, but alsofor optimized dwell times in the respective zones in the bath dependingon egg size, weight and the starting temperature of the particularbatches of eggs.

Certification of proper pasteurization requires verification checks onbath temperature and processing times to confirm that an approvedpasteurization protocol (e.g. verified to meet FDA standards) has beenemployed and that equipment is performing in accordance with theprotocol. While the prior art system allows the operator or supervisorto check the current status of the system and the temperature sensorsvia a connected computer 28, it does not provide data acquisition andreporting capabilities. Another object of the invention is to providedata acquisition and reporting capabilities in a manner that fostersthorough, convenient confirmation of batch compliance with approvedpasteurization protocols.

Also, in the event that the pasteurization process falls out ofcompliance for one or more batches, it is important that these batchesbe removed from downstream processing and packaging. Another object ofthe invention is to provide an on-site alarm signal that indicates tosystem operators when a batch needs to be removed from the processingstream.

SUMMARY OF THE INVENTION

The invention pertains to shell egg pasteurization systems that use abath filled with a fluid pasteurization medium, such as heated water,heated air, heated oil, or steam. In a preferred embodiment of theinvention, batches of shell eggs are sequentially moved in stagesthrough a series of multiple zones in the bath to pasteurize the eggs.As mentioned previously, however, many aspects of the invention can beimplemented in a system in which the batches of eggs are held in placesuch as in an incubator or a warming oven. In accordance with theinvention, a batch processing control system including, e.g. aprogrammable logic controller (PLC), is programmed to control both thetemperature of the fluid pasteurization medium and the period of time inwhich each batch of eggs is held in the heated fluid pasteurizationmedium during the pasteurization process. The dwell time and temperatureare controlled in accordance with a predetermined pasteurizationprotocol for batches of eggs having a designated size and starttemperature. The predetermined pasteurization protocol should bestatistically verified to ensure that the central portion of the eggyolk is heated to a sufficient temperature for a sufficient period oftime to achieve a desired, pre-selected reduction in salmonella speciespresent in the egg yolk for an egg having the designated size and starttemperature. However, the predetermined protocol should also bestatistically vertical to ensure that heating does not substantiallyaffecting the albumen functionality of the egg measured in Haugh unitscompared to the albumen functionality of a corresponding unpasteurizedegg. In the U.S., it is expected that the predetermined pasteurizationprotocol for time and temperature will be statistically verified toachieve at least a 5 log reduction in salmonella species for an egghaving the designated size and start temperature.

The invention facilitates the use of optimized dwell time andtemperature protocols for batches of shell eggs having various sizes,weights and start temperatures. The statistically verifiedpasteurization protocol defines one or more predetermined temperatureranges assigned to at least a portion of the total dwell time. That isto say, it may be desirable to hold the temperature of the fluidpasteurization medium at or near a constant temperature throughout theduration that the batch is in the bath undergoing pasteurization. On theother hand, it may be desirable to allow the temperature to fluctuate asthe batch of shell eggs proceeds through the various stages of thepasteurization process. In particular, it may be desirable to heat thefluid pasteurization medium to a higher temperature in the beginningstages of the pasteurization process than in the later stages of thepasteurization process. The programmed PLC controls the heating systemfor heating the fluid pasteurization medium in the bath in response tosignals from one or more temperature sensors located in the bath. In asystem in which the batches of eggs are moved sequentially through thebath, the programmed PLC also controls the motor advance to move thebatches of eggs from stage to stage and through the zones in accordancewith the predetermined protocol. In any event, it is desirable thatseveral predetermined protocols be available for implementation on thePLC, each being optimized for batches having a specified egg size andstart temperature.

In another aspect of the invention, the batch processing control systemincludes a programmable logic controller (PLC) that is programmed withone or more proportional-integral-derivative (PID) algorithms toprecisely control the temperature of the fluid pasteurization medium. Inthe preferred embodiment of the invention in which batches of eggs aremoved sequentially through various stages in the bath of heated fluidpasteurization medium, it is preferred that the system include multipleindependently controlled heating elements, each of which is controlledby a dedicated PID algorithm within the PLC. One or more temperaturesensors, such as a thermocouple is associated with each heating elementand is located in the fluid pasteurization medium in order to monitorthe temperature in the general vicinity of the respective heatingelement. The PID control algorithm for the heating element uses atemperature set point value defined by the predetermined pasteurizationprotocol being implemented on the PLC to operate the pasteurizationsystem. For each sampling cycle, the PID control algorithm receives atemperature feedback signal that is provided to the PLC from the atleast one temperature sensor associated with the heating element. ThePID control algorithm generates a control signal based on the differencebetween the temperature set point value defined by the predeterminedpasteurization protocol and the temperature feedback signal provided tothe PLC from the at least one temperature sensor. The control signal istransmitted from the PLC to an electronically controlled valve in orderto control operation of the respective heating element. It iscontemplated that a multiple zone pasteurization bath may include, e.g.,12 to 40 independently controlled heating elements. On the other hand,this type of control system can also be useful for controlling systemshaving few number of heating elements or even a single heating element.In any event, use of the PID control algorithms enables the system toclosely control the temperature of the fluid pasteurization medium sothat it remains within the preselected temperature range defined by thestatistically verified protocol.

As mentioned, in system in which the batch of eggs are movedsequentially through the bath, there can be a substantial temperaturedifference between the eggs and the fluid pasteurization medium, e.g.water, when a batch of eggs is initially placed in the first stage ofthe first zone. This temperature difference typically causes the firstzone to cool initially below the lower control temperature. While thereduced temperature in the first zone may not compromise the overallpasteurization process as long as the protocol compensates for thetemperature sag, the use of PID control algorithms and the ability toindependently control each of the various heating elements can helpreduce the magnitude of the temperature sag and accelerate temperaturerecovery. Also, the ability to hold the initial zone at a highertemperature than the remaining zones in the water bath may allow the useof pasteurization protocols having lower overall dwell time, therebyimproving system throughput.

As mentioned, the primary purpose of the first zone is to bring the eggsup to the pasteurization temperature preferably at or above 128° F.Salmonella species are destroyed primarily in the final three zones ofthe process, where the egg temperature is maintained at or near anoptimized pasteurization temperature. When determining the parametersfor the statistically verified pasteurization protocol, particular closeattention should therefore be paid to maintaining the appropriatetemperature in the zones downstream from the initial zone. With this inmind, bath temperature range and dwell time should be chosen for eachcombination of egg size (extra large, large, and medium) and batchstarting temperature (e.g. refrigerated at 45° F., or room temperature)in order to ensure full pasteurization without adversely affecting eggquality and functionality after pasteurization. The use of independentlycontrolled heating elements allows great flexibility in developing andobtaining optimized pasteurization protocols.

In accordance with another aspect of the invention, an on-site alarm isprovided at the exit of the pasteurizer. The alarm, for example a visualalarm such as a red light and/or an audio alarm, activates to indicatethat an exiting batch of eggs has fallen out of compliance with therespect to statistically verified protocol programmed on the PLC for thegiven batch.

Another aspect of the invention is directed to data acquisition andreporting. More specifically, a personal computer programmed withreporting software receives data, preferably on a real-time basis, fromthe on-site batch processing control system. The data communicationbetween the personal computer and the PLC for the on-site batchprocessing control system can occur in any number of manners known tothose skilled in the art. For example, the computer can be locatedremotely, and the communication can take place via the internet, or thecomputer can be located on-site. In addition, multiple computers cancommunicate with the PLC if desired. In accordance with the invention,the computer communicates with the PLC to gather reliable data regardingthe status of the pasteurization process for each batch of eggs beingprocessed. The data gathered for each batch of shell eggs includes abatch identification number or the like, an identification of the typeof batch (size of eggs, start temperature, etc.), the start time foreach batch, and the temperature of the bath in the zone that the batchis located at a particular time. Preferably, the computer software alsoallows the operator or a remote supervisor to also review the status ofequipment and components on site, including bath temperatures.

The software preferably generates a printable report containingcompliance data for all batches of eggs pasteurized for a given daythrough the pasteurizer. In its preferred format, the report tracks eachbatch through the pasteurization process, and importantly providesinformation that is needed to verify that each batch has been adequatelypasteurized. The report documents that each batch of eggs have beenexposed to the fluid pasteurization medium for an appropriate amount oftime within the predefined temperature range defined by thestatistically verified protocol for the appropriate egg size and starttemperature. The preferred report format includes average temperaturesfor the fluid pasteurization medium while the respective batch of eggsis located in each of the zones. In a preferred embodiment of theinvention, the report includes an indicator (such as check mark) ofwhether the temperature in any one of the zones has fallen out ofcompliance while a batch is located within that zone. The temperature ofthe first zone, of course, may not be as critical, because the primarypurpose of the first zone is to bring the eggs up to the pasteurizationtemperature whereas the primary purpose of the following zones is topasteurize the eggs. The report can be used to certify that batches ofshell eggs have been pasteurized in accordance with a relevant standard,e.g. the 5 log salmonella reduction standard mentioned above; and, inparticular pasteurized in accordance with a statistically verified timeand temperature protocol. Desirably, the data for each batch is alsoprovided in a graphical plot which includes a representation of thelower control temperature and the upper control temperature for thepreselected temperature range thereby providing convenient recognitionof whether the monitored temperature in one or more of the zones hasfallen out of compliance during the pasteurization process. In apreferred embodiment of the invention, the plot also includes an averagetemperature calculation for each batch which ignores the bathtemperature while the batch is in the initial zone and calculates theaverage based on the temperature in the remaining zones.

Other aspects and objects of the invention shall be apparent to those ofordinary skill in the art upon reviewing the following drawings anddescription thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a prior art temperature control systemfor an exemplary shell egg pasteurization system.

FIG. 2 is a schematic drawing illustrating the movement of batches ofeggs through multiple zones in an exemplary shell egg pasteurizationsystem.

FIG. 3 is a view taken along line 3-3 in FIG. 2.

FIG. 4 schematically illustrates a time and temperature control systemconstructed in accordance with the invention for use in the exemplaryshell egg pasteurization system of FIG. 2.

FIG. 4A is a schematic illustration of a PID algorithm used toindividually control a heating element in accordance with the preferredembodiment of the invention.

FIG. 5 depicts a computer report generated in accordance with thepreferred embodiment of the invention.

FIG. 6 depicts a data graph constituting part of the report illustratedin FIG. 5.

FIG. 6a is a detailed view of a portion of the graph in FIG. 6.

FIG. 7 illustrates a data chart constituting part of the report in FIG.5.

DETAILED DESCRIPTION

FIGS. 2 and 3 illustrate a shell egg pasteurization system 110 in whichbatches 112A through 112M of eggs are passed through four zones (Zones 1through 4) of a pasteurization bath 116. In commercial operations, it isnot efficient or cost effective to pasteurize a single egg, a single rowor even a single layer of shell eggs at a time. Therefore, it is knownin the art to pasteurize batches of eggs containing several stackedlayers of eggs. For example, a flat may contain 2½ dozen eggs, with astack containing four layers of flats and each batch containing 16stacks loaded onto a carrier 118A through 118M. Generally speaking, thebath 116 must heat not only the eggs, but also the flats and thecarriers. Even though the carriers 118A-118M and the flats are typicallythe same whether the eggs being pasteurized are medium size, large,ex-large or jumbo, the different size and weight of the eggs as well asthe potentially different starting temperature for the eggs in the batchwill normally impact the temperature in Zone 1 of the bath 116differently. Further, the weight of two different stacks of medium-sizedeggs is potentially different, and the same is true of the weight of twostacks of large eggs, ex-large eggs, etc. Therefore, even though thesame sized eggs are being processed, the effect that a given batch haswhen it enters the pasteurization bath 116 can vary.

As shown in FIG. 2, each zone in the pasteurization bath 116 includes afirst, second and third staging position, 120A, 120B, and 120C for Zone1, 122A, 122B, 122C for Zone 2, 124A, 124B, 124C for Zone 3 and 126A,126B, 126C for Zone 4. There are therefore 12 staging positions withinthe bath 116 shown in the embodiment in FIG. 2. FIG. 2 also shows acarrier 118M containing batch 112M of eggs prior to being placed in thebath 116, and carrier 118A containing batch 112A of eggs which has beenremoved from the bath at 116 after pasteurization. Note that thecarriers 118B through 118L containing batches of eggs 112B through 112Lare located within the bath 116 and have been moved forward one stage inpreparation for the bath 116 to receive carrier 118M and batch 112M inthe first staging position 120A of Zone 1.

As shown in FIG. 2, the fluid pasteurization medium, e.g. heated water,in the bath 116 is allowed to flow between zones inasmuch as Zones 1, 2,3 and 4 are physically continuous. It should be understood, however,that the schematic representation of the system 110 in FIG. 2 is merelyrepresentative of the types of systems on which the invention may beused, and that the invention may be useful with other types ofpasteurization systems. For example, it is well within the scope ofinvention to physically separate the zones of the bath into two or morephysically separate compartments. Likewise, the fluid pasteurizationmedium may be steam, heated oil, heated air, or some other heat transfermedium. Also, as mentioned previously, many aspects of the invention areapplicable to pasteurization systems in which the batches of eggs areheld in place throughout the entire pasteurization process, such as inan incubator or oven.

Referring still to FIGS. 2 and 3 in which the fluid pasteurizationmedium is water or some other liquid, sets of heating coils 128A through128D are located in each respective zone to heat the fluid within thezone. In accordance with preferred embodiment of the invention, each ofthe heating coils in each set of heating coils 128A through 128D arecontrolled independently. Temperature sensors 130A, 130B, 130C and 130D,such as thermocouples, are located in each zone of the bath 116. Asshown in FIG. 3, a thermocouple 130A through 130D is located in thegeneral vicinity of each respective heating element 128A through 128D.While the invention can be implemented with a single thermocoupleassociated with each heating element, one of ordinary skill in the artwill understand that it is possible to use additional thermocouples inthe vicinity of the respective heating elements for purposes ofredundancy and averaging. If the fluid pasteurization medium is water,it may be desirable to inject pressurized air into the bath 116, seeincorporated U.S. Pat. No. 6,113,961. The temperature sensors 130 areelectrically connected to a programmable logic controller (PLC) 132 forthe control system 134, FIG. 4.

FIG. 4 schematically illustrates a time and temperature control system134 constructed in accordance with the invention for a shell eggpasteurizer, such as pasteurizer 110 shown in FIGS. 2 and 3. Inparticular, the time and temperature control system 134 is a batchprocessing control system, that controls both the temperature of thefluid pasteurization medium 116 near the respective heating elements128A through 128D as well as the movement of the advance motor 135 toadvance the batches 112A, 112M from stage to stage and zone to zone. ThePLC 132 is programmed in accordance with a predetermined pasteurizationprotocol for batches of eggs having the designated size and starttemperature. Several prior patents including Cox U.S. Pat. No.5,589,211; Davidson U.S. Pat. No. 6,322,833; Vandepopuliere et al. U.S.Pat. No. 6,974,599 describe the importance of pasteurization time andtemperature. These patents as well as others namely Polster U.S. Pat.No. 5,993,886, discuss the importance of maintaining the internaltemperature of the eggs at an appropriate temperature for a sufficientamount of time to achieve a desired log kill rate of salmonella.However, shell egg pasteurization equipment in the prior art does notenable the operator to adjust the pasteurization time and temperature byprogramming the PLC with a protocol that is verified for batches of eggshaving a given size and start temperature.

The invention ensures appropriate pasteurization by operating theequipment in accordance with a statistically verified protocol forpasteurizing the eggs with the designated size and start temperature.The preferred way to statistically verify the pasteurization protocolfor time and temperature is to run tests in which sample shell eggs aretested during the process for temperature at the central portion of eggyolk as well as salmonella kill rate, and/or kill rate for otherpathogens if desired. It is expected that the pasteurization protocolfor time and temperature for the given egg size and start temperaturewill be statistically verified to maintain a central portion of the eggyolk at sufficient temperature level for a sufficient period of timenecessary to achieve the desired reduction in salmonella species, butinsufficient to substantially affect the albumen functionality of thepasteurized egg as measured in Haugh units compared to the albumenfunctionality of a corresponding unpasteurized egg. The pre-selectedreduction in salmonella species or other pathogen will typically be a 5log reduction in salmonella in order to meet the standards set by theU.S. FDA for a shell egg to be labeled as pasteurized, but may beanother level such as a 3 log reduction for jurisdictions having lowerstandards, or a 7 log reduction when higher standards are desired.

The PLC 132 preferably contains uploaded software in a machine readableform on a data storage device or in memory that is able to implement aplurality of predetermined pasteurization protocols, each beingstatistically verified, and each being customized for a distinctcombination of egg size and start temperature. For example, thecontroller 132 may contain six formulas: one pair of formulas for fullbatches of medium sized eggs with one at a start temperature of 45° F.and the other at a start temperature at room temperature; a second pairof formulas for full batches of large sized eggs with one formula for astart temperature of 45° F. and the other at a start temperature at roomtemperature; and a third pair of formulas for full batches of ex-largesized eggs again with one formula with a start temperature of 45° F. andanother formula for a start temperature at room temperature. Eachformula will likely have a unique dwell time, as well as one or moreunique target temperatures. For example, the total dwell time for abatch of medium sized eggs having a start temperature equal to roomtemperature may be 48 minutes, which means that each batch of eggsspends 12 minutes in each of the four zones as the batch 12 movesthrough the pasteurizer 116. In the system 110 shown in FIGS. 2 and 3,individual batches 118M would be placed within the pasteurizer bath 116every four minutes according to this hypothetical protocol, and eachbatch 118A-L would remain in each stage 120A-120C, 122A-122C, 124A-124C,126A-126C for four minutes. Referring again to FIG. 4, the PLC isprogrammed to hold each batch of shell eggs 112A-112M in each of therespective zones 114A-114D for a preselected period of time, and the PLC132 will transmit a control signal to the motor advance 135 accordingly.

FIG. 4 shows the PLC 132 controlling one heating coil 128, although itshould be understood that in the system illustrated in FIGS. 2 and 3that the PLC 132 will independently control each of the 12 heatingelements 128A-128D. As shown in FIG. 4, for each heating element 128,the PLC 132 receives a signal from at least one temperature sensor 130.In particular, an electronically controlled valve 138 controls the flowof heated water from the boiler 136 to the respective heating element128. In other words, there is a separate electronically controlled valve138 for each of the twelve heating elements 128. Referring to FIG. 4A,the PLC uses a proportional-integral-derivative (PID) algorithm, block139, to control the operation of each heating element 128 independently.For example, in the system shown in FIGS. 2 and 3, the PLC will beprogrammed with 12 separate PID algorithms to control the operation ofthe heating elements 128. The temperature of the fluid pasteurizationmedium in the vicinity of the respective heating element 128 iscontinuously monitored by the respective temperature sensor 130. Theloop time for the PID algorithm is preferably five seconds althoughother loop times may be used in accordance with the invention. PIDalgorithms are generally known in the art. The set point temperaturevalue for the heating element is defined by the predeterminedpasteurization protocol. The difference between the set pointtemperature value and the temperature feedback signal from thetemperature sensor 130 results in an error signal that drives the PIDalgorithm 139. The set point temperature value for the heating elementmay be constant throughout the entire dwell time, or may be defined bythe predetermined pasteurization protocol to vary with the dwell time.In any event, the error signal drives the PID algorithm to generate acontrol signal that is transmitted to the valve control 138. Theproportional aspect of the PID algorithm pertains to the severity of theerror gap and uses a constant to calculate the amount of time the valveshould be open to eliminate the gap. The integral aspect essentiallymeasures how long the error gap has occurred, and the derivative aspectmeasures the rate of change of the proportional aspect. Each of thesevarious aspects is combined to generate a control signal transmitted tothe electronic valve 138 for each cycle of the loop. Preferably, thecontrol signal is a value between zero and one and represents thepercentage of time that the valve 138 will be open for the 5 second loopinterval. For example, if the generated control signal from the PIDalgorithm is one, the valve will remain open to allow the flow of hotwater to the heating element 128 for the entire 5 second cycle. On theother hand, if the generated control signal is only 0.8, the valve willbe open for 4 out of 5 seconds. In this manner, the PLC 132 preciselycontrols the operation of each individual heating element 128, therebypreventing large swings in temperature.

Preferably, a separate PID algorithm is used to control the temperatureof the water supplied by the boiler 136, for example at about 170° F.

While the set point temperature value is a precise target value for thetemperature of the bath in the vicinity of the respective heatingelement 128, the predefined pasteurization protocol will normallyinclude a defined range, for example a half of degree Fahrenheit aboveor below the set point temperature value which is acceptable forimplementing the protocol. The use of the multiple individuallycontrolled heating elements is effective in maintaining the temperatureof the fluid pasteurization medium within the desired temperature range.If, however, the temperature in one or more areas of the pasteurizationbath approaches the upper control temperature, the PLC 132 will operatethe cold water flow valve 140 to add cold water to the bath. Typically,there will only be one cold water valve, although in accordance with theinvention there may be several. In any event, it is desirable that theoperation of the cold water valve be controlled by a separate PIDalgorithm in the PLC, and if the system includes multiple cold watervalves that each one be independently controlled.

The system also includes a level sensor 142 that senses the level ofwater in the pasteurizer. As in the prior art, if the water level dropsbelow the location of the level sensor 142, the PLC 132 will add coldmake up water by opening flow control valve 140. When this occurs, itwill also normally be necessary for the controller 132 to control theboiler 136 and hot water flow control valves 138 to provide hot water tothe heating coils 128 in order to maintain the temperature of the bathwithin the accepted temperature range for the given protocol programmedon the PLC 132.

FIG. 4 also illustrates a compressed air source 144 along with a controlvalve 146 to control the level of compressed air being supplied to thepasteurizer bath 114. The PLC 132 can optionally control the flowcontrol valve 146 for the compressed air in accordance with thepredetermined pasteurization protocol programmed on the PLC 132.

Several manufacturers make PLCs 132 suitable for this application. ThePLC 132 preferably receives data from and transmits data to operationalcomponents of the system (e.g. sensors 130, 142; valves 138, 140, 146;motor advance 135; boiler 136; and alarm 152, 154) at a sampling rate ofone sample per five seconds or faster. The PLC 132 preferably alsoincludes a communications port that is capable of communicating with aconventional personal computer 148. FIG. 4 shows the computer 148communicating with the PLC 132 via dashed line 150. It should beunderstood that the computer 148 may communicate by any number of meanswith the PLC 132, such as over an internal network, over an internetconnection, wirelessly, etc. In addition, while it may be desirable tohave the computer 148 on-site at the pasteurization facility, thecomputer 148 or one or more additional computers 148 may be locatedremotely. Typically, the computer 148 will have a display and a userinterface such as a keyboard and mouse or a touch screen whereas the PLC132 might not have a display and user interface. The PLC 132 willtypically be programmed via the communication link 154 between thecomputer 148 and the PLC 132. Preferably, the computer 148 will receivedata from the PLC 132 for each batch of shell eggs being pasteurized.Also, preferably real-time data from the temperature sensors 130A-130D,the status of the heating and/or cooling system, the flow rate ofcompressed air 146, and optionally the status of advance motor 135 areprovided to the computer 148 in real-time. The real-time data can beviewed on the remote computer 148, and can also be stored for later useif necessary. As discussed in more detail below, the data is alsopreferably analyzed and converted in order to generate compliancereports.

Commercially provided software for the computer 148 is desirably used toprogram the PLC 132. The PLC programming software should not only becapable of implementing the initial setup of the PLC 132 but also toselect an appropriate protocol corresponding to the egg size and starttemperature for the batches being processed. For example, one of thestatistically verified protocols will be chosen if batches of mediumsized eggs held at room temperature are being pasteurized. At start up,the PLC 132 will instruct the heating system to warm the pasteurizerbath to the appropriate target temperature for the chosen statisticallyverified protocol. The PLC 132 will then instruct the advance motor 135to move the batches of eggs in the pasteurizer bath 116 sequentially perthe chosen statistically verified protocol. The PLC programming softwareshould also be capable of transmitting collected data from the PLC 132over the communication's link 150 to the computer 148.

For each batch the reporting software on the computer 148 assigns abatch identification number, as well as the batch start time and anidentification of the batch type, namely egg size and start temperature.In addition, the reporting system on the computer 148 creates a writtenrecord of the temperature of the bath 116, and in particular thetemperature within the appropriate zone of the bath 116 when the batchis located in the zone. In a system in which the batches are not movedfrom zone to zone, but held in place within the pasteurization bath, thereporting software preferably records the average temperature of thebath for a given portion of the overall dwell time.

In the preferred embodiment of the invention in which the batches aremoved sequentially through the bath, the average temperature in the zoneover the time period that the batch is in the zone is calculated andrecorded for each respective batch and for each respective zone. Theprogrammed PLC 132 monitors the average temperature for each batch ineach zone, and determines when and if the average temperature in a zonewhile a batch is located in the zone exceeds the upper temperaturecontrol limit or falls below the lower temperature control limit.Alternatively, only the average temperature for each zone following theinitial zone 1 are monitored to determine whether the calculated averagetemperature falls between the upper control temperature and the lowercontrol temperature. If the average temperature falls out of compliancefor one or more zones, the PLC 132 activates a visual alarm and/or audioalarm to indicate that the batch is out of compliance. Referring to FIG.4, the system schematically illustrates a visual alarm 152 and an audioalarm 154. The preferred visual alarm is located at the downstream endof the bath 116 and includes a red 152R, yellow 152Y and green 152Glight. The illumination of the red 152R, yellow 152Y, and green 152Glights is controlled by the PLC 132. The green light 152G indicates thatthe system is operating properly. The yellow light 152Y indicates thatthe system is nearing the end of the cycle and that the advance motor135 will soon advance the carriers signaling that the operators of thesystem should get ready for further processing of the carrier 118A andbatch 112A being removed from the system at the end of the cycle. Thered light 152R is illuminated when the exiting batch 112A has fallen outof compliance, indicating that the batch should be removed from furtherprocessing. The audio alarm 154 can be used for a number of purposes,but preferably provides a unique audio signal corresponding to theconditions for illuminating the yellow 152Y and red 152R alarm lightsrespectively.

Referring to FIGS. 5 through 7, after collecting data from the PLC 132,software on the computer 148 prepares a printable report 156 indicatinga summary of the data for each batch of eggs pasteurized by thepasteurization system 110 for a given day. As illustrated in FIG. 5, thereport 156 is preferably a daily report, see reference numeral 158. Atthe top of the report 156, the pasteurizer for which the report pertainsis identified, see reference number 160. The overall purpose of thereport 156, as mentioned, is to track each and every batch of eggspassing through the pasteurizer and provide the documentation whetherthe batch was subjected to proper pasteurization temperatures for theproper amount of time for the given size and start temperature for theeggs. The reporting system is able to collect information from more thanone pasteurizer. The pasteurizers can be located at the same facility,or can be located at different facilities. In any event, the dailyreport 156 is preferably formatted so that it identifies the batchespassing through a given pasteurizer at a given facility, see referencenumber 160.

For each pasteurizer and each day reported, the start time and date andend time and date for the report 156 are indicated at the beginning ofthe report, see reference number 162. In addition, the starting batchidentification number and the ending batch identification number for thereport 156 are indicated, see reference number 164. The number ofbatches processed during the day are indicated on the report, seereference number 166, as is the averaged dwell time of the batches ofeggs in the pasteurizer, see reference numeral 168, and the averagetemperature of the bath while the eggs are in the pasteurizer, seereference numeral 170. The report includes a chart 172 which containsbatch specific information, and is shown in more detail in FIG. 7. Thedata in chart 172, or at least much of the data shown in chart 172, isillustrated graphically in graph 174 which is shown in more detail inFIGS. 6 and 6A.

Referring first to the chart 172 in FIG. 7, each batch is assigned achronological batch identification number, see first column in FIG. 7,and the start time and date for the batch is recorded, see second columnin FIG. 7. The third column in FIG. 7 lists the total dwell time thatthe batch was within the pasteurization bath. The fourth column in FIG.7 indicates the batch type. As described previously, the batch typedefines the choice of statistically verified pasteurization protocolbased on egg size and start temperature. Note that a change of egg sizeor start temperature in the exemplary system will require the system tofully process all the batches of eggs of the first batch type (e.g.medium sized eggs at a start temperature of 45° F.) before beginning toprocess eggs of a second batch type (e.g. large sized eggs at startingtemperature of room temperature). This is because the time andtemperature are optimized for the specific batch type, and statisticallyverified, to provide optimum pasteurization without comprisingfunctionality of the eggs.

The columns on the right side of FIG. 7 pertain to the temperature ofthe bath. The column labeled Zone 1 lists the average the temperature ofthe bath in Zone 1 while the respective batch was located in Zone 1. Theaverage temperature value is in fact an average of the temperature fromeach of the thermocouples located in Zone 1 and time averages for theperiod of time in which the batch is located in Zone 1. The averagetemperatures listed under the columns labeled Zone 2, Zone 3 and Zone 4are similarly calculated. To the left of the columns labeled Zone 2,Zone 3 and Zone 4 there is a column labeled C. The column labeled Ccontains a check mark to indicate that the temperature in that zone inthe pasteurizer while the respective batch was located in that zone wasin compliance with the statistically verified pasteurization protocolfor the batch type (egg size and start temperature). While the exemplarychart 172 in FIG. 7 shows that batch 2528 was out of compliance in Zone3 and batches 2431, 2532 and 2640 were out of compliance in Zone 4,under normal operation the vast majority of batches will be incompliance. The last column under the temperature heading is labeledaverage, and preferably contains an average of the temperature while thebatch is held in the zones downstream of Zone 1, namely held in Zones 2,3 and 4.

Referring now to FIGS. 6 and 6A, graph 174 plots the data listed inchart 172. The X-axis in FIGS. 6 and 6A identifies each individual batchby its start time. For example, the first batch in FIGS. 6 and 6Acorresponds to batch number 25-28 in FIG. 7 which has a start time of6:10 a.m. Referring in particular to FIG. 6A, which is a detailed viewof the leftmost portion of the graph 174 in FIG. 6, the graph 174includes an average temperature bar for each batch while the batch isresiding in the respective zone. In FIG. 6A, for each batch the leftmostbar represents the average temperature in Zone 2, the second barrepresents the average temperature in Zone 3, the third bar representsthe average temperature in Zone 4, and the fourth bar represents theaverage temperature in Zone 1. Note that the average temperature in Zone1 is substantially lower than the average temperature in the remainingdownstream zones, as should be expected unless the protocol is adjustedto account for initial heat loss when the batch is initially set in thebath. FIGS. 6 and 6A also preferably include lines 178 and 180 whichcorrespond to the upper control temperature and the lower controltemperature for the given protocol.

Of course, the format of the report 156 should be adjusted as necessaryif the protocol requires customized dwell times and temperatures. Forexample, in a system in which the amount of dwell time in the initialzone can be set to be different than the time in the downstream zones,the report should be changed accordingly. In addition, in the event thatthe selected protocol requires that the temperature at differentintervals during the total dwell require different target temperatures,the report should also be likewise adjusted in order to accommodate theapplicable protocol.

In the foregoing description, certain terms have been used for brevity,clearness, and understanding. No unnecessary limitations are to beinferred therefrom beyond the requirement of the prior art because suchterms are used for descriptive purposes and are intended to be broadlyconstrued. The different configurations, systems, and method stepsdescribed herein may be used alone or in combination with otherconfigurations, systems and method steps. It is to be expected thatvarious equivalents, alternatives and modifications are possible withinthe scope of the appended claims.

What is claimed is:
 1. A shell egg pasteurization method, comprising theacts of: providing a bath containing water, wherein the bath comprises aseries of zones; providing a batch carrier arrangement for advancingbatches of shell eggs through the zones of the bath; sensing thetemperature of the water in each zone of the bath; providing a heatingsystem for selectively raising the temperature of the water in each zoneof the bath, wherein the heating system includes at least oneindependently controlled heating element in each zone of the bath;providing a cooling system for selectively lowering the temperature ofthe water in the bath; providing a pressurized air supply system incommunication with the bath and operating the pressurized air supplysystem to flow air into the bath; and operating a batch processingcontrol system according to a pasteurization protocol selected from aplurality of predetermined pasteurization protocols, wherein eachpasteurization protocol is based on a designated size and starttemperature of shell eggs in a batch and sets a temperature set pointvalue for the water in the bath, an upper temperature limit for thewater in the bath that is higher than the temperature set point valueand a total dwell time in the bath for the batch, wherein the act ofoperating the batch processing control system comprises: selecting apasteurization protocol for a batch of shell eggs; controlling operationof the heating system to independently raise the temperature of thewater in each zone of the bath toward the temperature set point for theselected protocol in response to the act of sensing the temperature ofthe water in each respective zone; selectively operating the coolingsystem to lower the temperature of the water in the bath in response tothe act of sensing the temperature of the water, to maintain thetemperature of the water below the upper temperature limit establishedby the selected pasteurization protocol; and controlling movement of thebatch carrier arrangement through the series of zones of the bath tohold each batch of shell eggs in the water for a total dwell timeselected in accordance with the selected pasteurization protocol.
 2. Theshell egg pasteurization method as recited in claim 1, wherein eachpredetermined pasteurization protocol for time and temperature isstatistically verified for maintaining a central portion of the egg yolkat a temperature level for a period of time necessary to achieve a 5-logreduction in Salmonella species present in the egg yolk in order tothoroughly pasteurize an egg having the designated size and starttemperature.
 3. The shell egg pasteurization method as recited in claim2, wherein the act of controlling operation of the heating system iscarried out by circulating heated fluid through a coil-type heatingsystem in each zone.
 4. The shell egg pasteurization method as recitedin claim 2, wherein the act of selectively operating the cooling systemis carried out by introducing cold water into the bath.
 5. The shell eggpasteurization method as recited in claim 2 wherein each of theindividually controlled heating elements comprises a heating coillocated in one of the zones of the bath and an electronically controlledvalve associated with the respective heating coil to control flow ofheated water through the respective heating coil, and wherein the batchprocessing control system comprises a programmable logic controllerwhich is programmed with a proportional-integral-derivative algorithmfor each of the individually controlled heating coils, each saidproportional-integral-derivative algorithm using a temperature set pointvalue defined by the selected predetermined pasteurization protocol andreceiving a temperature feedback signal provided to the programmablelogic controller from a temperature sensor associated with therespective heating coil, and each of saidproportional-integral-derivative algorithms generates a heating controlsignal that is transferred from the programmable logic controller tocontrol operation of the respective heating coil.
 6. The shell eggpasteurization method as recited in claim 2 wherein the batch processingcontrol system controls an advance motor to move the batch carrierarrangement and thereby the respective batches of shell eggs through andbetween zones in accordance with the selected predeterminedpasteurization protocol for the batches of shell eggs being pasteurized.7. The shell egg pasteurization method as recited in claim 2 furthercomprising providing data from the batch processing control system to acomputer for each batch of shell eggs being pasteurized, said dataincluding a batch identification number, an identification of the typeof batch based on the size and start temperature of the shell eggs inthe batch, the batch start time, and the temperature of the water inwhich the batch is located per time period of the pasteurizationprocess, and further comprising the act of operating the computer toprovide a printable report indicating the data for each batch of eggspasteurized for a given time period.
 8. The shell egg pasteurizationmethod as recited in claim 7 wherein the report contains data for allbatches of shell eggs pasteurized through the system for a given day. 9.The shell egg pasteurization method as recited in claim 8 wherein theprintable report contains a plot that graphically depicts the time andtemperature of the water in which each batch is located per time periodof the pasteurization process.
 10. The shell egg pasteurization methodas recited in claim 2 wherein each said predetermined pasteurizationprotocol sets a lower temperature limit in addition to the uppertemperature limit and the temperature set point for the water and themethod further comprises the act of operating a sensory alarm located ator near an exit of the pasteurization bath, the alarm providing anon-site sensory indication when an exiting batch falls out of compliancewith respect to the upper temperature limit, the lower temperature limitor the total dwell time of the selected predetermined pasteurizationprotocol.
 11. The shell egg pasteurization method as recited in claim 1wherein the pressurized air supply system comprises a source ofpressurized air and a flow control valve and each pasteurizationprotocol sets a level of compressed air flowing into the bath, andfurther wherein the act of operating the batch processing control systemfurther comprises controlling operation of the flow control valve inaccordance with the selected pasteurization protocol to control thelevel of air flowing into the bath.